i've recently purchased this nice 4x5 developing tank that fits about twelve, but i'm having a little difficulty because- to be honest- i've hardly had to mix up the chems developing film, only when it's necessary. but anyways, i'm not sure how much i'll need for the 55cc that it needs, and i dont know how much mL of HC-110 i i have to have. can anybody help me out?

HC-110 is supplied in different concentrations, so you need to consult the bottle or set of instructions to determine how to make the dilution you require. The best starting point is Dilution B which is considered the "standard" dilution for this developer